Directive 2010/31/EU (EPBD) indicates that EU Member States must ensure that by 2021 all new buildings, and already by 2019 all new public buildings, are nearly zero-energy buildings (NZEBs). Article 2 of the EPBD defines the term NZEB as a building with a very high energy performance and a nearly zero or very low amount of energy required, which itself is covered to a very significant extent from renewable sources. The detailed definition of NZEBs in practice is the task of the Member States, and shall be reported in the national plans for increasing the number of NZEBs. Now, in mid-2015, and therefore at about half of the foreseen implementation phase, it might be a good time to find out whether the countries have implemented case studies of NZEBs and which strategies and technologies have been utilised in order to fulfil the foreseen national NZEB requirements. The examples have been collected in the context of the Concerted Action EPBD (CA EPBD) initiative.
Concerted Action EPBD
The CA EPBD is the meeting point for representatives of national organisations working on the implementation of the European Directive on the Energy Performance of Buildings (EPBD). The initiative facilitates structured and confidential dialogue between the delegates, in order to contribute to the better understanding of implementation challenges and of advantages and disadvantages associated with the various implementation strategies. The majority of the activities are not public, but the CA EPBD regularly publishes books and reports. The CA EPBD also cooperates closely with BUILD UP, e.g. for the section “Country Fact Sheets”.
One of the most recently released publications of CA EPBD is the report “Selected examples of Nearly Zero-Energy Buildings”, which compiles 32 examples of buildings implemented in EU the set (or envisaged) NZEB national requirements. The examples have been selected and provided by CA EPBD national delegates.
International examples of NZEBs
Pilot projects of nearly zero-energy buildings are built to show the public, as well as the involved industry and planners, that buildings of this kind are already possible, what they look like, what costs are implied, which technologies can be used and what are the user experiences. The examples, which are presented in the report in a structured way, have been contributed by the Member States delegates of 20 countries in total. They include residential and non-residential buildings, new buildings, as well as renovations to the NZEB level. In the following pages a few of the case studies are shortly described to show the rather different approaches.
This newly built housing complex is, with a net floor area of about 21.000 m², the largest of the collected NZEB examples. The multi-family house has been constructed with a thermal building envelope that meets Passive House requirements, including triple-glazed windows. The complex is heated by a district heating system, while the domestic hot water demand is mainly covered by a 700 m² solar thermal collector installed on the roof. Part of the energy concept is a mechanical ventilation system with 75% heat recovery. The total final energy use for heating, domestic hot water and ventilation amounts to 30,1 kWh/m²/year and includes 52% renewable energy contribution. The overall performance goes beyond the current Austrian energy performance requirements by 43%.
The architectural approach, with a variety of shared spaces including a swimming pool on the terrace, combined with the extensive infrastructure results in a very high residents’ satisfaction level. The building costs were 57 million EUR for the entire estate which amounts to about 2.700 EUR/m², partly subsidised by the Styrian government.
The Bulgarian case study proves that very low energy consumption can be achieved with moderate renovation measures at the building envelope level (insulation of the walls to reach a U-value of 0,35 W/m²K, 10 cm mineral wool insulation between the ceiling and the unheated space under the roof to reach 0,26 W/m²K, and new double-glazed windows), combined with a comprehensive improvement of the building service systems. The heating and cooling of the research centre is now achieved by an ambient-based variable refrigerant flow heat pump in connection with the ventilation. Hot water is provided by local electrical heaters and the building now also features a low-energy lighting system. The total final energy use includes heating, domestic hot water generation, cooling, ventilation, and lighting amounts to 48 kWh/m²/year. This is an improvement of 78% compared to the national requirements in Bulgaria. Sixty-three percent (63%) of the final energy is provided by renewable energy sources. The measures have required up to 38 EUR/m² for the renovated building envelope and 92 EUR/m² for the Heating, Ventilation and Air-Conditioning systems and 130 EUR/m² for the lighting. Total costs were 423.900 EUR (for 1.630 m²).
The Croatian NZEB example was a pilot project to specifically demonstrate that the national energy performance class A (foreseeing less than 15 kWh/m²/year for heating) can be met. It is a three storey multi-family house with 28 apartments. The walls have been insulated with 20 cm stone wool, the roof with 30 cm XPS and the windows are triple-glazed. Heating and cooling are provided by an underfloor system connected to a reversible heat pump and a gas boiler. A ventilation system with a high recuperation factor ensures good indoor air quality. The domestic hot water is generated by solar thermal collectors in combination with the gas boiler. The total final energy includes heating, domestic hot water, cooling, ventilation and lighting and amounts to 66 kWh/m²/year, which is 78% lower than the national building energy performance requirements. Twenty two percent (22%) of the final energy is provided by the solar thermal collectors. The most impressive factor about this pilot project is that it was built without any additional costs compared to a regular building fulfilling the national requirements. The total costs amounted to 912 EUR/m². One area found lacking was the insufficient experience of the workforce concerning the application of new technologies, especially the mounting of the windows which should meet a quality control scheme used in Germany (RAL). Further information about the national status and possibilities of training the workforce can be found under BUILD UP Skills.
This Swedish example is one of many high performance single-family houses presented in the report, several of which aimed much further than the national NZEB requirements (plus energy or net zero energy), and proved thus also much more expensive (e.g. the German efficiency house plus in Berlin). The single-family house in Vallda is highlighted as one example where the additional costs, compared to a regular Swedish single-family house, are only 10% higher – with the total cost reaching 4.360.000 EUR or 2.450 EUR/m². It is a building in an area where all buildings have to aim for the Swedish passive house standard. The timber stud walls have been insulated with 29 cm mineral wool and 8 cm glass wool (U=0,11 W/m²K), while the roof includes 60 cm blowing wool (U=0,07 W/m²K) and the house has triple-glazed windows. There is a supply and exhaust ventilation system with a rotating heat exchanger and a heating element. The bathroom floor heating system is connected to the domestic hot water system. Both heating and domestic hot water are supplied by a local district heating system with 40% of the energy generated by solar thermal energy and 60% by a central wood pellet boiler. The measured total final energy use amounts to 56 kWh/m²/year and is 100% renewable. The improvement compared to the national energy performance requirements is 51%. The project shows a very good conformity with the calculated values at the planning stage and the residents are very satisfied with the indoor climate.
Cross analysis of the applied strategies and technologies
Two-thirds (22) of the gathered buildings concern residential and 11 non-residential buildings, whereby 25 are newly built and 7 renovated to the NZEB level. Building sizes vary considerably between 98 m² and 21.000 m². The construction types include brick, concrete and timber walls with U-Values between 0,065 and 1,97 W/m²K and an average of 0,29 W/m²K. Roof U-values are generally lower with 0,06 to 0,55 W/m²K and an average of 0,14 W/m²K. Twenty (20) buildings have low-e-coated triple-glazed windows and 8 buildings, mostly located in Southern Europe, have double-glazed windows.
Fourty one percent (41)% of the examples are heated by heat pumps; other heat generators often used are gas boilers, district heating and biomass boilers. Only 32% of the buildings include cooling systems which often use activated building components. The domestic hot water system is nearly always combined with the space heating system, but four buildings use decentralised electrical domestic hot water generation. About 77% of the buildings use mechanical ventilation systems with heat recovery, and only 3 buildings rely solely on natural ventilation.
As regards the renewable energy sources, PV panels have been installed in 69% of the examples and solar thermal systems in 53% of the buildings. Geothermal energy contributes via heat pumps in 31% of the buildings, while six additional buildings use air-to-air heat pumps (ambient energy). The district heating systems that are connected to the buildings often show a high share of renewable energy and therefore low non-renewable primary energy factors.
Measured energy values are available for 8 of the 32 buildings; in the remaining cases, values have been calculated usually with the national energy performance calculation method. Nine buildings achieve a positive annual primary energy balance, the so-called ‘plus energy buildings’. For seven of them, this includes also the equipment, e.g. household energy, etc. The average renewable energy ratio related to the total final energy is as high as 70%, and the average improvement of the presented examples over the current national requirements is also very high at 74%.
Cost data has been difficult to compare as the buildings differ in the aimed energy levels, size, building type, and, most importantly, country of origin. For several buildings (in particular those that are privately owned) costs are not available; for others, costs are expressed in different ways, e.g. total costs, additional costs for achieving the high energy performance, total EUR, or percentages. The costs may also include different cost items. However, a first analysis of cost data, based on nine example buildings each, shows that the additional construction and technology costs for NZEBs compared to buildings fulfilling the national energy performance requirements are between 0% (0 EUR/m²) and 25% (473 EUR/m²), with an average of 11% (210 EUR/m²). Two-thirds of the buildings have received special funding to cover part of the planning, construction or monitoring costs.
Documented experiences with the buildings include high owner satisfaction, monitored energy use that meet the calculated predictions, advices on how to further increase the energy efficiency or comfort in the buildings, and experiences with certain building materials. Many of the buildings received architectural or energy efficiency awards. The CA EPBD report gives insights into all 32 inspiring examples and more details on the cross analysis.
Conclusions and future
The CA EPBD catalogue of selected examples of NZEBs shows that there are pilot projects for NZEBs and demonstration projects of even more ambitious energy performance levels in at least 20 Member States. Since most of them are residential buildings, it can be assumed that many countries started the NZEB application in the domestic sector, to continue in the non-residential in the coming years. The decrease in energy consumption compared to the current national energy performance requirements for buildings (74% in average), and the ratio of the renewable energy use (70% in average) are more than impressive. The quality of the used building envelope and applied building service technologies depend on the countries but some main approaches can be reported as follows: low U-values at the roof (with an average of 0,14 W/m²K), mostly triple-glazed windows in Central and Northern Europe, heat generation by heat pumps, gas boilers or district heating systems with high ratios of renewable energy, ventilation systems with heat recovery and PV and solar thermal systems. The additional costs range from as low as zero compared to a standard building to an average of 10% higher.
In the coming years all countries will have fixed their national application of the NZEB definition and this will open the way for further pilot and demonstrations buildings with different technical approaches and more experiences with costs and user satisfaction.
The Energy Community, an international organisation dealing with the energy policy in 6 Western Balkan countries, Moldova and Ukraine, is working together with the EU with a focus on the import of the EU energy policy into the non-EU countries. The current situation of the Former Yugoslav Republic of Macedonia, Kosovo, Moldova, Montenegro and Serbia related to NZEBs is described in the countries’ reports on implementation of EPBD from 2013/2014. So far there is however limited use of the possibility to develop targets and plans for increasing the number of NZEBs. The Work Programme of their Energy Efficiency Coordination Group (EECG) for 2015-2016 foresees activities on harmonized development of the NZEB concept and action plans and the promotion of existing EU applications and concepts. They will report on NZEB targets, available NZEBs and plans in the next round of the NEEAPs in June 2016.